


The Knife in the Dark

by Allegra Tale (Wingsister_Miri)



Category: Harry Potter - J. K. Rowling, Poirot - Agatha Christie
Genre: F/M, Murder Mystery, and not that graphically, everybody has something to hide at Hogwarts, just the corpse, no actual death portrayed
Language: English
Status: Completed
Published: 2014-04-17
Updated: 2014-04-17
Packaged: 2018-01-19 18:26:26
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 9
Words: 7,420
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1479595
Author URL: https://archiveofourown.org/users/Wingsister_Miri/pseuds/Allegra%20Tale
Summary: <blockquote class="userstuff">
              <p>Hercule Poirot, an old friend of Dumbledore's, is called in when everyone's favourite potions professor is murdered.</p>
            </blockquote>





	1. Chapter 1

**Author's Note:**

> I wrote this story as a birthday present to my father. I hope you can enjoy it too!

Hercule Poirot was reclining in his favourite armchair when he heard a soft tapping coming from the window. When he opened it, a nondescript brown owl fluttered through and landed on the table. It dropped a letter into Poirot’s outstretched hand and hooted softly.

The detective returned to his armchair and broke the seal on the heavy parchment envelope. Nowadays, he hardly ever received sealed letters since most his clients preferred to telegraph their requests for assistance to him.

The letter was short and to the point:

_My dear Monsieur Poirot,_

_We have had a most disturbing incident at Hogwarts. One of our teachers, Severus Snape, was killed last night, stabbed in the back._

_I would be very glad if you would consent t clear this matter up for us. I have little faith in the authorities, as they would likely search only for ways to implicate me in this matter. They have tried to destabilize my position for a long time._

_I hope we will welcome you at Hogwarts soon._

_Yours sincerely,_

_Albus Dumbledore, Headmaster_

Poirot leaned back in his armchair and thought the matter over. It was likely a very simple problem, but it must have some interesting features if Dumbledore felt he was unequal to the task of finding the murderer himself. He decided he apparate to Hogsmeade and walk up to the school the next morning.

Poirot was met in the Entrance Hall by Professor McGonagall and escorted to the headmaster’s office. Dumbledore sat behind a big oak desk.

“Would you like a butterbeer, or perhaps a little firewhiskey? The journey can be very cold this time of the year”, Dumbledore offered, opening a drawer in the cabinet on the wall behind him.

Poirot accepted a butterbeer and started sipping it slowly while Dumbledore laid out the facts of the case before him.

“We haven’t had much crime within the walls of Hogwarts for the last few years, so this was a surprise for us”, he began.

“It was young Mr. Malfoy of Slytherin House who found him this morning on his way to breakfast. You see, Professor Snape was teaching Defense Against the Dark Arts this year instead of Potions, but he kept his old office in the dungeons.”

“When Mr. Malfoy found him, he was alone, lying in the corridor with a knife in his back. The door to his office was wide open and Professor Snape lay across the threshold.  Mr. Malfoy went to the Hospital Wing to fetch Madam Pomfrey, our nurse. She put the time of death between 10pm and midnight, when everyone was supposed to be in bed.“

“We left the body as it was and the corridor was closed. We put a stasis spell on the body so you can examine it in the state Madam Pomfrey found it in.”

Monsieur Poirot was very grateful for Dumbledore’s foresight in preserving the body as it had been found. Many of his cases would have been easier if he had had a chance to examine the body before it was removed from the crime scene.  But Dumbledore was not yet finished with his account.

“The knife in his back we left as well”, Dumbledore continued, “so it was hard to identify it, but we think it must be one of the knives Professor Snape used in his potions work. Though he is now employed in a different position, he has continued with his potions research.“

“The students have not yet been told of this incident, they have merely been told that their Defense classes are cancelled for the time being. I daresay”, he added with a wry smile, “that some of them are very happy about it. Professor Snape was not a well-liked teacher. Very strict, you see, especially towards members of houses other than Slytherin.”

Dumbledore stood up and gestured towards the door.

“We have prepared one of the offices on the first floor for your use, but I expect you will want to see the body first?” he asked.

Poirot nodded affirmatively. “You have not mentioned magic?” he asked.

“No, that is the queer thing.” Dumbledore sighed. “No magic was used at all. If it had been magic, we might easily have traced the spell-caster ourselves. But considering the circumstances, we thought it more prudent to call in an expert on muggle murders than to make a muck of it ourselves”, he chuckled. 


	2. Chapter 2

Poirot let him lead the way to the body. On the way, they met Madam Pomfrey, the nurse, who was asked to accompany them to the body.

The Belgian detective felt a tingle as he passed through the barrier protecting the corridor from prying eyes. Students could not enter the scene of the crime, which was probably a good thing as the Professor’s murder would otherwise have drawn many gawkers.

As he knelt beside the body, Poirot noticed a liquid spilled on the floor. It was a deep red, so at first sight it might have been mistaken for blood, but it was still fluid, unlike the congealed blood on the Professor’s back.  

“What is this?” asked Poirot, “Some kind of potion?”

“Yes”, provided the helpful Madam Pomfrey, “it is a strong sleeping potion. It should not be treated lightly. Large doses of the potion could probably kill a person, or at least send them into a coma.”

Poirot took a look at the knife sticking out of the victim’s back a little to the left of the spine. It had a long black carved handle, some sort of runes apparently. Part of the blade was also visible, it had a silvery shine underneath the blood and seemed to be carved with the same symbols as the handle. There was even a small crossguard, making the knife seem more like a small dagger. The knife had a very dark look about it; it almost seemed like a thing that would be used in a ritual of dark magic.

“Is the knife used for specific potions only or is it for general use?” asked Poirot, though he doubted the latter would be the case.

“It certainly does look strange”, asserted Madam Pomfrey, “but I don’t know about its purpose, I have never seen a knife like that before. You will have to ask Professor Slughorn, our Potions Master.”

Monsieur Poirot thanked her as he carefully wrapped the knife in his handkerchief and put it away in his pocket. He asked her and Professor Dumbledore to tell no one about the strange knife, should they have to tell anyone about Professor Snape’s death. The information could be important, after all, and Poirot did not want rumours spreading about the Professor’s death having been ritualistic. It would only lead to panic if people speculated about a cult killing people.  

Professor Dumbledore by his side, he climbed the stairs to the office that would be his for the duration of the investigation. It was a well-appointed room lit by torches held in decorated sconces along the walls. The furniture was plain but looked comfortable. Poirot’s eye was immediately drawn to the enormous polished desk that dominated the room. If he needed it, it would make an imposing setting for interviews with suspects.

“Lunch should be almost ready”, said Dumbledore, “if you will sit by me in the Great Hall I will tell you more about the case and the people involved in it, should you require that.”


	3. Chapter 3

In the Great Hall, Monsieur Poirot sat down to Dumbledore’s left. The magical ceiling was a stormy grey, threatening rain. The atmosphere seemed gloomy and somber, even though the student body had not yet been told of Professor Snape’s demise.

Poirot had been travelling all morning, so he had a healthy appetite. The lunch served by the house elves was excellent, but Poirot’s thoughts kept returning to the poor Professor Snape. Something was wrong about the way he had lain in the corridor, but the ex-auror could not quite pinpoint what it was.

To distract himself, he started conversing with Professor Slughorn, who was seated beside him.

“Terrible, my dear chap, that’s what it is, Poor man never had many friends, but that someone would just come up to murder him, bold as you please, is just incomprehensible to me. “, Professor Slughorn started expounding.

“Makes one fear for one’s own safety, of course. Strangers breaking into Hogwarts, the safest place in Britain, and murdering people. What has this place come to?”

“So you believe this was the work of strangers?” Poirot prompted him, “but could no one in the castle have done this? I hear he was not well liked?”

“Well, no, he was never very popular, neither among the students nor among the teachers. But I can’t believe this of my colleagues, and surely Severus would have been perfectly capable of defending himself against one of the students?”

“Ah! Thank you, mon ami!” exclaimed Poirot. “You have made me realize something very important. Now, who do you think might have wanted the professor dead outside of Hogwarts? The opinion of those who knew him is very important, as you know. Often they have insights into things a detective might never be told about the victim, because it might seem insignificant to the authorities.”

The Potions Master seemed very enthusiastic at being asked these important questions.  A little flattery will loosen all tongues eventually, though Professor Slughorn certainly wasn’t the most difficult challenge in that department.

The professor leaned closer to Poirot and lowered his voice: “There were rumors, you know. Dreadful rumors about Severus still having a connection to the Death Eaters, despite Dumbledore vouching for him ... The headmaster will not tolerate Snape being talked about in this way, of course, but I wouldn’t be surprised if there wasn’t a little bit of truth about it. Maybe one of the members of the Order of the Phoenix found out he was a spy and wanted to protect the Order from him? That’s what I imagine the reason to be, anyway. This is all in strict confidence, of course, wouldn’t want to be heard spreading these dreadful rumors, of course. It is always perilous to get mixed up in these things.”

Poirot murmured his assent and assured the professor of his discretion. On being asked about the knife, Professor Slughorn told Poirot that such a knife could have many uses, but that its most common application was in the preparation of both poisons and strong medicines. The detective made sure that Professor Slughorn would not release this “extremely confidential” information to anyone. The Potions Master seemed very flattered because he was allowed to know more than the general public. 

After the excellent lunch Poirot decided to mingle with the teachers for a while longer. He had faith in Hogwarts’ defences and did not believe any outsiders could have broken in undetected.  So his thoughts turned to the teachers. Could any of them have killed Severus Snape? He decided that they probably could have had the opportunity and the strength to drive the knife in his back, but did any of them have the motive?


	4. Chapter 4

When he arrived in the staff room, Professors McGonagall and Sprout were already discussing the case.

The Head of Hufflepuff House was absolutely shocked by the gruesome crime that had happened in the school. Professor McGonagall was attempting to calm her down, but she hadn’t succeeded so far. Professor Sprout seemed close to tears, so Poirot addressed the transfiguration teacher first.

She was outraged at such a violent crime happening in _her_ school, but did not seem particularly sad about her colleague’s death.

“Well,” she said when Poirot asked her about it, “usually I try not to think too badly of my fellow professors, but Severus really crossed the line. Neville Longbottom, a boy from my House, had a nervous breakdown because of him only last week. Everyone knew he wasn’t fair towards students of houses other than Slytherin, but to actually harass the poor boy until his mind saw no other way out than to simply shut down is just unforgivable to me.

That is the reason I am not particularly grieved right now. I am sure that will change once this has had a chance of properly sinking in, but at the moment I am only glad the same thing won’t be happening to any other students.”

“Where is the boy now, Professor?” inquired Poirot, “would it be possible to speak to him?”

“I expect so; he seems to be recovering well, especially since his grandmother has arrived.”

“Just as a matter of routine… Could you tell me where you were during the last night, approximately between 9 and 10 pm?”

“Of course,” she answered, “I suppose you must ask everyone? I was patrolling the school with Pomona here. Since last year, the Death Eaters have increased their efforts to break into the school. There was an alarm last night, but when we got to the wards, we did not see anyone and apparently nothing had gotten in. We checked the area but went back to patrolling when we did not find anyone.”

Poirot thanked her and turned to Professor Sprout, but she didn’t have anything to add except the vague feeling of having heard someone near Gryffindor Tower and a long lament about what the world was coming to now one could wake up one day with a knife in one’s back.

Poirot doubted she had really heard anything that night. Witnesses often fancied having heard strange noises or cries after hearing that a murder had been committed on a particular night. However, it wouldn’t do to dismiss her out of hand, even if Professor McGonagall hadn’t heard anything.

After this, Monsieur Poirot had half an hour’s painful conversation with Sybil Trelawney, the teacher for Divination. She had not seen or heard anything, not having left her tower in quite a while before hearing of Professor Snape’s murder, so she was useless as a witness, yet she insisted on telling the detective of the many death-omens she had seen regarding her colleague.

“Oh, I always said he’d come to a terrible end, but that clueless centaur would not believe me when I wanted to discuss the signs with him. Laughed me out of his office, he did. That ignorant horse!” Apparently Professor Trelawney could think of no worse insult for her fellow Divination professor. She was still very bitter about having to share her classes with him.

“But I was right!” she continued. “I foresaw this. The same strong signs as that Potter boy. Ooooh yes, I will show that Firenze who’s the _real_ Seer.”

Here Poirot had to enquire: “You have also seen death omens connected to Harry Potter?”

“Oh yes, of course.” She replied. “His omens have always been very strong, since he was a little boy. Did you know,” she whispered conspiratorially, “that I saw a grim in his tea leaves in his third year? And you know, he has been in mortal danger every year since. It is only a matter of time before the omens will be fulfilled and he meets the same fate as the unfortunate Severus Snape.”

Poirot feared she would start off on a diatribe on what was obviously her favourite topic, so he asked:      

“Do I understand you correctly? You think there is a connection between the murder of Professor Snape and the hopefully far-off death of Harry Potter?”

“But of course,” she answered, “there is always a connection where there is strong emotion. They despised each other, hated each other. That is a very strong feeling. I thought everyone knew that?”

Poirot thanked her for her time. He had indeed not known about this fact, which was apparently common knowledge at Hogwarts. He resolved to ask Dumbledore about it later.

 


	5. Chapter 5

Next he went up to the Hospital Wing to ask Madam Pomfrey a few questions. When he arrived, she was bustling around a bed that was hidden behind curtains to protect the privacy of the patient and his family. Poirot quietly sat down in Madam Pomfrey’s office. He could hear the nurse talking to Neville Longbottom’s grandmother.

“Your grandson will be fine, Mrs. Londbottom!” said Madam Pomfrey, “I am glad that all he needs are a few weeks’ peace and quiet. He should probably also try talking to a psychologist at St. Mungo’s. Talking about his experiences, remembering them in a safe environment, might help him with regaining the memories he has lost. I know it looks bad right now, with his blackout episodes, but he really will be all right.”

Augusta Longbottom thanked her in a very stiff manner and turned back to her grandson’s bedside.

When Madam Pomfrey found Monsieur Poirot in her office, she was surprised to hear that he had apparently forgotten his questions for her. She watched him leave with a pensive expression on his face.


	6. Chapter 6

Monsieur Poirot decided he would make use of his impressive office to interrogate a few of the students.

First he had Harry Potter brought to him. He could easily see that the boy was not exactly happy at being singled out like this.

“You wanted to see me?” he asked, his face screaming defiance. “Sir?” he added sullenly.

“Yes, my dear boy, do have a seat,” replied Poirot, “do you know why you are here?”

“I really don’t. Professor Dumbledore said to cooperate with you, but he didn’t say on what.

“Then,” said the Belgian detective gravely, “it is my sad duty to inform you that Professor Severus Snape was murdered yesterday night between nine and ten pm.”

At this, Poirot could clearly see the conflicting emotions on the boy’s face. First there was surprise, apparently no rumours had trickled through to the students from Draco Malfoy. The Slytherin had been told not to breathe a word to the other students, but Poirot had not really believed that a student could resist the urge to show off that he knew more than his classmates. But maybe this information had just not penetrated the Gryffindor/Slytherin barrier.

Then, Harry Potter’s face betrayed shock, probably because he still believed that everyone was safe at Hogwarts, despite the evidence to the contrary provided by his own adventures.

Next, there was a sort of savage glee. This disturbed Poirot. A boy so young, only 16 years old, should not have that much hate inside him.  Though Poirot had to concede that Harry Potter had had much more danger to deal with than any normal teenage boy, so that might be the reason for his violent emotions.

In a flash, it was over and Harry Potter’s features were blank again.

“So,” asked Poirot, “you do not seem too sad about your teacher’s demise?”

“No. The whole school knew we hated each other. The world is probably a better place without him. Did you hear about what he did to Neville? No. I am not sad that he died. But that doesn’t mean I killed him, if that’s what you’re implying.” The boy answered, defiance seeping out of every pore. His attitude seemed to dare Poirot to contradict him, but the Belgian detective just ignored it.

“Could you tell me where you were last night between nine and tem pm? You understand that I have to ask this of everyone who might have the slightest motive for killing him.”

“That’s everyone in the school. Not even the Slytherins were happy with him anymore. He started treating them almost as badly as the rest of us; he even took points off them. I was in the Common Room with Ron and Hermione all night, working on our homework.” 

But Poirot was not convinced. There was a slight hesitation in the way he said it, and the boy had looked down when he said it, when before he had always met Poirot’s gaze head-on.

“Could you tell me who else might have wanted to kill Professor Snape?” Poirot asked.

“Well, you might try Draco Malfoy. He was always Snape’s favourite, but as I said, Snape started docking points even from him. And Malfoy’s up to something. I’m sure he works for Voldemort. He keeps sneaking around, maybe Snape found out about it and wanted to stop his plans, or something like that?”

Poirot could see that Harry wanted this theory to be true. There seemed to be a grudge between the boys that went further than normal house rivalry. The detective thanked the boy and let him go.

Poirot decided to follow him to check whether his account of the previous night had been true. He was certain the boy had been lying, but he had nothing to prove it. The boy went towards the Great Hall to dinner, but Poirot turned towards the Gryffindor Common Room. On the way he met Hermione Granger and Ron Weasley coming down the stairs, as he had hoped he would.

“Excuse me, Mademoiselle,” he called to her, “excuse me, I seem to have lost my way. I arrived yesterday, but I still can’t remember the way to the Great Hall. Could you kindly point me in the right direction?”

“Of course,” she answered, “you can just come with us, we’re on our way there now.”

“Have we met before, Miss…?”

“Hermione Granger,” she supplied helpfully, “and this is Ron Weasley.”

“Ah, yes, I remember now. You and that nice Mr. Potter showed me the way back to my quarters last night, I afraid I would have to wander the corridors all night.”

“Oh no,” she contradicted him, “I was in the Common Room all night, with Ron. But Harry wasn’t there, you could have met him with someone else.”

“Of course, I am so forgetful nowadays. You must be right. Excuse me.” And with those parting words, he turned right into a corridor and left Ron and Hermione behind.

They looked after the little man with a baffled look on their faces. He was almost bouncing along the corridor; so much spring was there in his step.

They shrugged and headed on to dinner, still talking about the little man with the strange moustache.


	7. Chapter 7

After dinner, Poirot cautiously opened the door to the Hospital Wing and peered inside. Neville Longbottom was alone, his grandmother nowhere to be seen. The Belgian detective slipped inside and went over to Neville’s bed. He sat down on the chair that had only recently been vacated by Augusta Longbottom.

“Hello,” he greeted Neville, “would you mind if I asked you a few questions? Have you heard about Professor Snape?”

“Yes,” said Neville, seemingly absentminded. “Harry came in before and told me about it. I think I haven’t really realized it yet. I think I should be sad or glad or just feel _anything,_ but I just don’t feel it at all, like it is just a story and not really true at all. Is it?”

“It really is true, Neville, never doubt that. So Madam Pomfrey told me you were recovering well. When will you be allowed to leave the Hospital Wing?”

“Madam Pomfrey said I could leave tomorrow. Finally. I’ve felt strong enough to leave for a few days now, but she always said I had to stay in my bed, under observation, for a few more days. She always tries to do this to her patients, but with Harry for example she usually doesn’t have a chance, he gets on her nerves until she lets him leave. I wish I was as good at that as him. I’m going crazy locked up in here. I don’t know where my gran got the energy to look after me night and day, just sitting in here all day. Madam Pomfrey had to send her away to get some sleep.”

Neville wasn’t really sure why the strange man was here, just sitting with him and twirling his moustache, but he was glad he had someone there to talk to now his grandmother wasn’t here anymore.

“I’m sure she doesn’t mind, Neville. All grandmothers I know enjoy looking after their grandsons. Can you tell me what caused your illness? Was it a specific event or just too much stress over a long period of time?”

“Well,” said the boy, sinking down lower under his covers, as if hiding from the memory, “I felt I was under a lot of pressure since the summer holidays because of what happened last year. I was at the Ministry with Harry and the others when we fought the Death Eaters, you know? My gran was really proud of me, for the first time I wasn’t a failure compared to my father. She even told me I reminded her of him and gave me his wand after mine was broken. I just wanted her to be proud of me; I didn’t want to be a failure anymore.”

Neville’s eyes started watering, he looked close to tears. Poirot laid a hand on his shoulder and tried to soothe him. “All grandmothers I have ever met have been proud of their grandsons. Going to the Ministry and fighting Death Eaters far more experienced than you, that took a true Gryffindor’s courage.”

“Look at me, blubbering at the first person to talk to me. I’m sorry, maybe it’s because I don’t know you. Anyway, I tried _so_ hard in all my classes this year. And I got much better in most of them, and Hermione helped me a lot. But in DADA, nothing worked. Snape just kept humiliating me, even though I got much better. And then I did a spell completely wrong and hit Hermione accidentally and Snape took 50 points off of me, and I was really worried about Hermione. And then I just blacked out and I don’t remember anything after that.

Then I woke up here and Harry told me Madam Pomfrey had already fixed Hermione and she was all right. I was just _so_ relieved. But I kept blacking out and not remembering stuff I’d done. My gran was really worried. But this morning Madam Pomfrey said I’ll be all right. We were so relieved.”

Everything Neville said came out in a rush, like he couldn’t stop himself from telling someone all his fears, yet wanted it to be over as quickly as possible.

“I am glad to hear you will be all right, Neville. Now, what I really came here to ask is if you have any idea as to who might have killed Professor Snape. Anything at all, no matter how insignificant it might seem to you, might be of immense help to me.”

Neville looked surprised at being asked his opinion in such an important matter.

“Well, maybe…” he started slowly. “I can’t imagine he’d really do it. You can’t take my word for it, I don’t think he could actually kill him just like that. But if it’s really important… You know Sirius Black died at the Ministry last year? He was Harry’s godfather. That was really important to Harry, because he doesn’t know his family, you know? And Hermione told me Harry blames Snape for what happened to Sirius. I mean, Snape was always taunting him and if he hadn’t, maybe Sirius would have let the others handle the fight at the Ministry. Snape was always saying that Sirius was a coward for not going out. But what was he supposed to do, let himself get kissed by the Dementors?”

“Of course not, Neville, I understand. I am glad you decided to tell me, and I will not tell anyone where I got this information.”

At this point, Augusta Longbottom stormed through the doors, a look of anger on her face. “They tell me Snape is dead. Good riddance, I say! And he didn’t even have the decency of finishing those medicines for you before he died.”

“Mrs. Longbottom, I am Monsieur Poirot. Professor Snape was making medicines at the time of his death? For your grandson? Would you mind telling me what kind?”

She glared at him. “I don’t see how this is any of your business, but he promised me he could make a potion to restore Neville’s memories. I even got him a special ritual knife so the work would go smoothly. He assured me it was necessary for the potion because it was a very strong medicine. And then I come here and find out he’s been killed with it. And now my grandson,” she fixed Poirot with an icy glare, like this was somehow his fault, “has to go to St. Mungo’s to be treated instead. It will take him away from his school and his friends for weeks. All because someone stabbed Snape in the back. So now tell me, what are you doing here when Neville should be resting?”

Monsieur Poirot mumbled an apology and excused himself, fleeing from the formidable matriarch. He stopped by Madam Pomfrey’s office to ask her a few questions.

Of course she had a way of tracking her patients, she told him. If she didn’t, some of them would never stay in their beds. She had to know when Harry Potter or one of the other troublemakers was making another attempt at escape of course. So far, no one had figured out that she put a tracking spell on all those admitted to her care, and the miscreants were always surprised when she turned up at the last moment to thwart their escape plans. Yes, she did have a recording of the map for the last few days, though she was surprised that he asked. Yes, if he was that interested in the system, of course he could take a quick look, that wouldn’t hurt anyone, surely?

Happy with his success, Monsieur Poirot left the Hospital Wing.

 


	8. Chapter 8

Monsieur Poirot went back to his temporary office and called for Draco Malfoy. Harry Potter had been convinced the Slytherin had murdered his Head of House, maybe there really was something to that. Even if the boy was completely innocent, he was the one who had found the body, so he might have noticed something that others had not.

When Draco Malfoy entered the room, Poirot could see that getting information from this boy would be much harder than getting it from Harry Potter had been.

“Hello, Mr. Malfoy. My name is Monsieur Poirot. I would like to ask you a few questions about his morning. You found the body, did you not?” he began.

“Yes, I did.” Malfoy answered, but it was obvious that he would rather not talk to the Belgian detective.

“So? Please tell me about it in your own words; it would be very helpful for me. I am attempting to find his murderer, so any information at all is helpful.” prompted Poirot.

“I woke up, got dressed, went to breakfast and on the way there I saw him lying in the corridor. There was lots of blood so I didn’t touch him, he was obviously dead. So I went to Dumbledore. He told me not to tell anyone and that was it. Can I go?”

“Not quite.” Poirot sighed. “I need to know where you were last night between nine and ten pm.”

“I was in detention with Filch. You can ask him. Having it that late was his idea; I think he wanted me to get into trouble on the way back. Hogwarts has servants. They are for cleaning the potions cauldrons, not me. This school is just getting worse and worse. Next we’ll have to cook our own meals.” He scoffed.

Poirot had heard enough. The boy would obviously not volunteer information, and now he could check whether he had really been in detention the previous night. He would verify that information the next morning, he was too tired to do it now.

On his way back to his sleeping quarters Poirot bumped into Harry Potter, who was obviously so lost in a daydream that he barely noticed the little man who had run into him.

“Ah, Mr. Potter, just the young man I was looking for,” Poirot called after him. “Might I have a word?”

Harry turned around, startled. “What about? You said you had no more questions earlier.”

“True, but that was earlier, this is now. Tell me, why did you lie about having been in the Common Room last night? I know you weren’t. If other people find out you lied about your whereabouts, they will think you murdered Professor Snape. I don’t think you did, so why don’t you tell me what you were really doing?”

“How do you know I didn’t kill him? Everyone seems to think I did, because the whole school knows we hated each other. Harry was clearly weighing the option of telling the detective what he knew, but he hadn’t made his mind up yet.

“Harry, you are a Gryffindor. I have heard about your adventures at school, of course. Who hasn’t? You always seem to be the kind of person who faces a problem head-on. If you had challenged Professor Snape to a duel and killed him in a fair fight, I would not have been very surprised. But Professor Snape was stabbed in the back. That tells me he didn’t think his murderer could harm him, otherwise he would never have been surprised with his back turned and he would have defended himself.”

This seemed to convince Harry that Poirot really didn’t think that he was responsible.

“Fine, I’ll tell you,” he said. “I was, I was … well, I was seeing a girl.” His face turned bright red and he looked down, shuffling his feet. “Ginny and I have been seeing each other for a while now, but her brother, Ron, can never know. He’s my best friend, but he’d kill me if he found out. So we’ve been sneaking out so he wouldn’t find out.”

Poirot chuckled. “Your secret is safe with me, Mr. Potter, I won’t breathe a word.” Harry thanked him and went on his way.

If it had been Mr. Potter and his girlfriend sneaking around that Professor Sprout had heard, then he ought to have all the puzzle pieces by now. He just needed time to let his little grey cells do the work and put the puzzle pieces together.

The next morning, when everyone was assembled at breakfast, Dumbledore announced to the students that Professor Snape had been murdered. Immediately, there was an uproar as the students began arguing amongst themselves. Poirot could hear many subjects being discussed: Why Snape might have been killed, whether their classes would resume now and who the new teacher would be, and of course the biggest question: Who was the murderer, and would there be another victim?

Poirot listened as Dumbledore attempted to calm the students down, but clearly the headmaster wasn’t making much headway. Only the knowledge that the perpetrator was caught would calm the students – and their speculations – down.

So it was time to gather all the people involved and reveal the murderer.


	9. Chapter 9

After breakfast, an excited group met in Hercule Poirot’s temporary office.

Harry Potter, Ron Weasley and Hermione Granger sat in a corner together with Neville Longbottom and they were furiously debating the case.

A little distance away was Augusta Longbottom, her attention focused on her grandsoneven while she was talking to Professors McGonagall, Sprout, Flitwick and Slughorn, who was representing Slytherin. 

Draco Malfoy sat alone, looking pale and apparently sulking, once in a while glancing at the other occupants of the room.

The only one missing was Professor Dumbledore, but just as Poirot was beginning to wonder where he was, he arrived, apologizing for his lateness. Apparently he had been held up by reporters, who had somehow gotten wind of the incident already, and the headmaster was none too happy about it.

“Now that we are all assembled,” began Poirot, “we can begin. My name is Monsieur Poirot and Professor Dumbledore has asked me to investigate the murder of Professor Severus Snape. We are meeting here because the killer is still on the loose, so we must find him … or her. There have been many rumours flying around, and I have attempted to either verify or refute them. ”

“I bet it was Malfoy!” he heard Harry Potter whisper to his friends. “I always said he’s up to something. Maybe Snape found out and tried to stop him.”

“It is, in fact, not Mr. Malfoy,” answered the detective. “If Mr. Malfoy was really “up to something”, an investigation into a murder would only increase his chance of being detected. Besides that, Mr. Filch assures me that Mr. Malfoy did not leave his sight once during the relevant time window. So you see, he could not have done it.

I also ruled out outsiders breaking into Hogwarts to murder him. A breach in the wards like that would have been detected by now. No, it was someone from inside the castle.”

Here Dumbledore sighed and rested his head in one hand, covering his eyes. The headmaster did not want to believe that one of his own had committed such a gruesome deed.

“So it is Potter!” jeered Draco Malfoy. “There is a betting pool in Slytherin Common Room over when you finally snap, Potter, and go insane. I bet sooner, what with your Mummy and Daddy dying so _tragically_ and leaving you with the nutjob muggles.”

Harry tried to jump out of his chair and rush at Malfoy, but Ron and Hermione grabbed him and pulled him back. It was obviously a maneuver they had had to practice dozens of times.

“Leave it, Harry.” Hermione quietly said to him. “He’s just trying to get a rise out of you. Do you really want to give him what he wants?” Harry sat back down, still glaring daggers at Draco Malfoy. If looks could really kill, the Slytherin would have died a hundred times over for mentioning Harry’s parents to him.

Professor McGonagall had watched the altercation quietly, but now she spoke up: “Ten points from Slytherin, Mr. Malfoy, for trying to provoke fighting.”

Poirot stood up and started pacing the room. “Actually, there is a good reason why neither of these boys could have stabbed Professor Snape in the back. It is precisely because he was stabbed in the _back,_ and there was no sign that he had tried to defend himself. I have heard Professor Snape was a cautious man, one might even say paranoid. He would not have turned his back to anyone he thought could do him any harm, especially since he was alone with the killer.  Besides this theory, Harry Potter can account for his movements during the relevant time period, which rules him out the same way as Draco Malfoy.”

As Neville Longbottom had listened to Poirot’s explanations, he had become pale and started to shake. His grandmother went over to him immediately and laid a hand on his shoulder.

“Sir… sir, it’s not… it’s not me, is it? Because I can’t remember everything I did…”

The boy looked close to tears, so Poirot quickly reassured him. “No, Neville, it was not you. Madam Pomfrey puts a tracking spell on all her long-term patients so they can’t just flee from the Hospital Wing without her knowing about it. She checked her records for Professor Snape’s time of death, and you were in your bed that night, and nowhere else.

The killer was actually someone no one here seems to have considered: Your grandmother, Augusta Longbottom.”

The room erupted into activity. If apparating on the Hogwarts grounds had been possible, Mrs. Longbottom would have been gone within half a second. As it was, she sprang up from her chair but was magically restrained by Professor Dumbledore before she had made two steps towards the door. She stood still, her feet seemingly glued to the floor, incapable of running away.

She drew herself up, staring Poirot in the eye proudly. “You cannot possibly prove that. Why would I have wanted to do that? He was making a potion for Neville, one that would have restored his memory, closed the gaps. I had no reason to want him dead.”

“Of course you did. He had terrorized your grandson until he had a nervous breakdown. That is reason enough for anyone. Professor Snape would have seen you as a grieving little old lady, and would not have hesitated to turn his back to you. A foolish move. Little old ladies are among the most dangerous creatures on earth, especially if you have wronged them as he had wronged you.

But, most damning of all, you knew what knife Professor Snape had been killed with when you came to the Hospital Wing, as you were the one who brought it to Hogwarts and killed him with it. No one but Professor Dumbledore, Madam Pomfrey, Professor Slughorn and me knew about the elaborate knife, and they all assured me that they would tell no one of it.”

Neville was staring at his grandmother in disbelief. “Gran? Did you really do it?” he asked. He looked absolutely shocked.

Augusta Longbottom drew herself up, looking around her, radiating pride.

“Yes. I did it. And I would do it again. I did it for you, Neville. You were so much happier since last year. You were so brave, going to the Ministry and fighting the Death Eaters. You were so confident since the summer holidays, and then that, _that_ _monster_ goes and takes it all away.” She was becoming visibly agitated.

“It was his fault you were in the Hospital Wing. I confronted him, and he said he could help me, could help you. He promised me a potion to counteract your memory loss. He asked me to get him the special dagger, said that without it, making the potion would be impossible. So I got it for him.

I went to Knockturn Alley, paid a shady dealer a lot of money, and I got it for him. And then, Snape tells me it is _impossible!_ Then why did he send me on that wild goose chase in the first place? Instead, he offered me an experimental sleeping potion. Drinking that would have put you into a _coma_ , Neville! He promised the coma would be healthy, that you could work through the trauma in it and be fine when you woke up. But I had enough of his promises.”

“Ah, that must have been the red potion that almost looked like blood.” Poirot muttered to himself.

“He was the reason for your breakdown,” continued Mrs. Longbottom, “and then he gave me hope and stabbed that hope in the back, figuratively of course. So I stabbed him in return. _Literally._ And I must say, I do not see how what I did was wrong. He won’t be doing any more harm to children. The world is a better place without him in it.”

This seemed to be all she wanted to say. There was a stunned silence in the room until Professor Snape sighed heavily.

“I wish this weren’t necessary, but justice must be served. Much as I understand your reasons, killing another human being is never an option. I will see to it that you get a fair trial.” Dumbledore seemed very old and tired all of a sudden. “I suggest everyone else go back to their duties.”

Harry, Ron and Hermione escorted the distraught Neville out of the room, and everyone else trickled out after them, returning to their normal lives. Only Professor Dumbledore, Monsieur Poirot and Augusta Longbottom were left behind. Poirot understood Mrs. Longbottom’s reasons, but because of her actions, Severus Snape was dead and would never get to return to his life, normal or not.

Professor Dumbledore tool Mrs. Longbottom’s wand from her and warded the room so she could be kept there until the Ministry officials could arrive. The headmaster and the detective left Augusta Longbottom sitting in her chair with a straight back, proudly fixing them in an icy stare.

When they were outside, Dumbledore sighed. “I am glad you found out murderer, Monsieur. I just wish it had been someone else. Will you stay for lunch or leave for London right away?”

“I think I shall stay and enjoy another excellent Hogwarts lunch. Shall we retire to your office and go over the fine points of the case together?”

They walked down the corridor together, discussing the best strategies for getting Augusta Longbottom a lenient sentence so she could soon be reunited with her grandson.

 

 

THE END

**Notes for the Chapter:**

> The final chapter! I hope you were at least a little surprised by the true culprit!


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